Desynchronization of Large Scale Delayed Neural Networks

We consider a ring of identical neurons with delayed nearest neighborhood inhibitory interaction. Under general conditions, such a network has a slowly oscillatory synchronous periodic solution which is completely characterized by a scalar delay di erential equation with negative feedback. Despite the fact that the slowly oscillatory periodic solution of the scalar equation is stable, we show that the associated synchronous solution is unstable if the size of the network is large

Multi-scale analysis on the role of mechanical loading in prenatal skeletal development

There is little understanding on how cell division, expansion and migration drive joint morphogenesis. Mechanical loading is known to affect joint morphogenesis, but the effects of mechanical loading on the cellular level are yet to be explored. Mechanical loading in utero comes mainly from muscle contractions and the resultant movements. However, passive movements may also play a role in skeletal development, particularly when muscle contractions are absent, but the effects of passive movements on the skeleton have not been well characterised. This doctorate aimed (1) to develop a robust method for analysing high-resolution cell-level data of developing joints, (2) to investigate the cell-level processes contributing to joint morphogenesis, (3) to identify the mechanoregulated cell-level processes, and (4) to explore the effects of passive movement on skeletal development. This research used embryos of wild type mice and “muscleless-limb” mutant mice from the Splotch-delayed line with a mutation in the Pax-3 gene. Aims (1–3) were achieved with ACCESS, an original automated image processing method that qualitatively and quantitatively analysed the properties of cells in murine distal humeri. The cell properties investigated included number, volume, sphericity, orientation and density. Proliferation and ECM contents were also quantified. Aim (4) was achieved by giving pregnant mice wheel exercise and therefore inducing passive movements in the embryos. Forelimbs of the embryos were scanned in 3D and rudiment length and mineralisation were quantified. For the first time, cell number and volume were reported as being key to the growth of a murine joint. Cell volume, orientation and proliferation were mechanoregulated. Wheel exercise affected forelimb rudiments significantly and could restore the length of some rudiments in muscleless-limb mutants. This research showcased new analytical and experimental methods adaptable for wider purposes, and advanced our knowledge for joint morphogenesis on the cell-level, especially relating to mechanoregulation.Open Acces

Land Use Rights, Government Land Supply, and the Pattern of Redevelopment in Shanghai

This paper reviews the urban redevelopment activities in Shanghai as the land market reforms were introduced. We focus on the impact of land use institutions on the spatial pattern of these activities. Sites for private real estate redevelopment were supplied by individual districts in the city. But the need for districts to pay for the resettlement of displaced residents contributed to a spatial mismatch between the supply of redevelopment sites and the market demand for commercial real estate space. Resettlement costs are highest at the high demand locations. State owned enterprises and institutions occupying land allocated by the state also engaged in real estate development. Whereas the density of private redevelopment was sensitive to the volume of commercial activities in a district, this does not appear to have been important in determining the location of the significant increase in the stock of commercial space resulting from development by local enterprises and institutions. This growth shows considerable decentralization between 1993 and 1996,indicative of spatially inefficient redevelopment activities by land-rich state enterprises.Institutions, Land Market, Economic Transition, Urban Redevelopment, Shanghai

Community Detection and Improved Detectability in Multiplex Networks

We investigate the widely encountered problem of detecting communities in multiplex networks, such as social networks, with an unknown arbitrary heterogeneous structure. To improve detectability, we propose a generative model that leverages the multiplicity of a single community in multiple layers, with no prior assumption on the relation of communities among different layers. Our model relies on a novel idea of incorporating a large set of generic localized community label constraints across the layers, in conjunction with the celebrated Stochastic Block Model (SBM) in each layer. Accordingly, we build a probabilistic graphical model over the entire multiplex network by treating the constraints as Bayesian priors. We mathematically prove that these constraints/priors promote existence of identical communities across layers without introducing further correlation between individual communities. The constraints are further tailored to render a sparse graphical model and the numerically efficient Belief Propagation algorithm is subsequently employed. We further demonstrate by numerical experiments that in the presence of consistent communities between different layers, consistent communities are matched, and the detectability is improved over a single layer. We compare our model with a "correlated model" which exploits the prior knowledge of community correlation between layers. Similar detectability improvement is obtained under such a correlation, even though our model relies on much milder assumptions than the correlated model. Our model even shows a better detection performance over a certain correlation and signal to noise ratio (SNR) range. In the absence of community correlation, the correlation model naturally fails, while ours maintains its performance

FreeU: Free Lunch in Diffusion U-Net

In this paper, we uncover the untapped potential of diffusion U-Net, which serves as a "free lunch" that substantially improves the generation quality on the fly. We initially investigate the key contributions of the U-Net architecture to the denoising process and identify that its main backbone primarily contributes to denoising, whereas its skip connections mainly introduce high-frequency features into the decoder module, causing the network to overlook the backbone semantics. Capitalizing on this discovery, we propose a simple yet effective method-termed "FreeU" - that enhances generation quality without additional training or finetuning. Our key insight is to strategically re-weight the contributions sourced from the U-Net's skip connections and backbone feature maps, to leverage the strengths of both components of the U-Net architecture. Promising results on image and video generation tasks demonstrate that our FreeU can be readily integrated to existing diffusion models, e.g., Stable Diffusion, DreamBooth, ModelScope, Rerender and ReVersion, to improve the generation quality with only a few lines of code. All you need is to adjust two scaling factors during inference. Project page: https://chenyangsi.top/FreeU/.Comment: Project page: https://chenyangsi.top/FreeU

Intelligent manipulator with flexible link and joint: modeling and vibration control

This paper presents a finite-element (FE) model of a manipulator with a flexible link and flexible joint as well as embedded PZT actuators and proposes a corrected rebuilt reduced model (CRRM) to make its dynamic characteristics more consistent with reality and facilitate control design. The CRRM considers the holding torque of the manipulator driving motor and eliminates the response divergence induced by a fault of the mass matrix of the FE model. In order to reduce the dimensions and maintain the precision of the model, an iterated improved reduction system (IIRS) method is adopted. Additionally, a LQR controller is designed based on the output function of the improved model. The simulation results demonstrate that the CRRM is consistent with reality and the active controller has good performance in suppressing vibration of the manipulator with both the flexible link and the flexible joint